Today, there is an increasing demand for the use of semiconductor laser devices using nitride semiconductors for large-capacity high-density optical disk systems which are capable of recording and reproducing a large volume of data such as DVDs. For this reason, enthusiastic study is being done on semiconductor laser devices using nitride semiconductors. The semiconductor laser devices using nitride semiconductors are considered to be capable of oscillating and emitting a wide range from the ultraviolet region to visible wavelengths including the red region and they are expected to have a wide range of applications including not only light sources for the above-mentioned optical disk systems but also light sources for laser printers, optical networks and the like.
Semiconductor laser devices require resonator faces for producing resonance of light from an active layer within a semiconductor layer and defining a waveguide region as an essential constituent for emitting a laser beam. The resonator faces can be formed by means of cleavage, etching, polishing and the like, which are selected as appropriate according to material. For example, in case of semiconductor laser devices using GaAlAs, GaAlAsP, GaAlInP and the like grown on GaAs substrates, which are capable of emitting light at long wavelengths such as infrared, red and the like, the resonator faces are often formed by cleavage, taking advantage of cleavability of the GaAs substrates.
On the other hand, nitride compound semiconductors are often grown on hetero substrates such as sapphire (Al2O3) that do not have cleavability. In the case of such substrates, it is difficult to form the resonator faces by cleaving the semiconductor layer with the help of the cleavability of the substrates, and therefore, the resonator faces are often formed by etching. For obtaining chips thereafter, the substrates are split by applying physical force through a means of scribing and the like because it is difficult to etch sapphire substrates.
The resonator faces are provided with reflective films for is improving light-reflectivity. In the case where division into devices is made through cleavage, it is easy to form uniform reflective films on entire end faces because the end faces of the devices including the resonator faces have a single plane. However, where the resonator faces are formed by etching, there is a problem in that satisfactory reflective films are often not formed because the end faces are uneven. For this reason, there is a problem in that, even if the resonator faces of the semiconductor layer have an excellent mirror surface, output can be poor according to the quality of reflective films formed on the resonator faces. There is also a problem in that a laser beam can be blocked because of the uneven end faces and the far field pattern (FFP) can be disturbed.